cmd/jujud: use appropriate timeout for run tests

Use LongWait for assertions of events that are
expected to occur, as described in testing/constants.go.

Fixes https://bugs.launchpad.net/juju-core/+bug/1362990
Merge pull request #637 from axw/lp1362990-cmd-jujud-runtests-timeout

cmd/jujud: use appropriate timeout for run tests

Use LongWait for assertions of events that are
expected to occur, as described in testing/constants.go.

Fixes https://bugs.launchpad.net/juju-core/+bug/1362990